I guess it sorta defeats the point since you wanted a menthol vape but I would consider switching out the menthol for Koolada. You will still get the coolness in your throat but woo it the "minty" taste of the menthol which might work a bit better for lemonade. they recommend using only a few drops of Koolada per something like 10ml but you may find its better at something like 1% if you want it really "cool."

Also you could try a dash of raspberry in it for "pink" lemonade.

Bonus recipe, TFA tutti frutti and VAP menthol go together quite nicely. Think about 6% TF and 2% M is what I used.

Try some fa bergamot if you want the citrus to punch thru the sweetness a bit more.

Strawberry could be a nice addition

you could add some mango or pineapple, works great for the summer

If you like the flavor, but want some more cool, just add .5-1% koolada on top. If you feel like it needs some more high lemon tartness you could add1%flavor express lemon and if it needs more sweet middle range lemon you could add 1%FA lemon sicily. Bergamot was already said, but it would work well for a mid range too.

2% FE Lemon or 1% FA Bergamot for a citrus tang, 2% FA Citrus Mix(lower Lemonade by 2%) for a tangy lemon lime, 2% TFA Quince with 0.5% koolada will make it a soft lemonade, more like a cold can of squirt....shit I should try this with FLV Pink Grapefruit